GIS Tech News #11

Minnesota county uses geospatial data to track trail of murder case suspect -- and ultimately put him in jail

On the morning of May 12, 2004, the trial for
Troy Mayhorn, a 25-year-old Chicagoan accused of aiding and abetting in the
shooting death of Nasean Jordan, began with opening statements from both sides
in Clay County Courthouse, in Moorhead, Minnesota. Prosecutor Lisa Borgen's
arsenal included a series of PowerPoint slides showing the locations of several
calls made from the defendant's cell phone during the time of the murder.
The visuals were constructed using data that indicates the locations of
cell towers that facilitated the calls. Pinpointed on a map and played back
chronologically, the data looked like virtual footsteps leading to and fleeing
from the crime scene.

That crucial piece of evidence was the work of Mark Sloan,
Clay County GIS coordinator, who shares a busy office with four staff
members on the third floor of the same courthouse building. Sloan spends most
days scrutinizing the AutoCAD files he receives from architecture firms and
updating property records and land parcels.

A fan of Robin Cook's suspense novels, Sloan welcomes the chance
to help local law enforcement whenever he can. When "The District" was still
airing on television, once in a while a police commander or a squad leader
would call Sloan to ask if he and his staff could do what the fictional police
chief Jack Mannion did using sophisticated GIS tools. (For more on that subject,
see "Philadelphia Police Use GIS to Combat Crime.") Sloan
could usually accommodate these requests, provided the resources he had were
sufficient and the scenario was not something made possible by cinematic trickery.
Generating high-resolution maps for detectives and tactical teams has become
a part of his job.

Towering Evidence
Sloan has worked with county attorney Lisa Borgen before. He sometimes
uses his expertise to prove that a drug-related crime has been committed
within 300 feet of a school, for example, allowing the prosecutor to seek
a heavier sentence under Minnesota law.

For the Mayhorn case, Borgen needed to first convince the grand
jury, and later the trial jury, that the suspect and his associates traveled
from Chicago to Moorhead to commit the crime. After she subpoenaed their
cell phone records, she noted that several calls registered around the time
of the murder. So she called Sloan and asked, "If we've got cell phone records,
can you figure out where the calls were made from?"

"What I received was raw cell phone records," says Sloan. "I've
never seen anything quite like that." Buried in the data were codes identifying
each cell tower that transmitted each call. Cell towers are registered with
the FCC and compiled into a searchable database, which proved a valuable resource
for Sloan in this case. Using cell tower IDs, Sloan was able to query FCC's
database and obtain the locations of the towers used.

Digging for Gold
As county GIS chief, Sloan had access to the data for Clay County but
not for Chicago, across the state line from Moorhead, Minnesota. He had to
hunt for the data he needed from several public sources; consequently, he
had the unenviable task of consolidating the data that existed in various
formats.

"Some were in lat/long (latitudes/longitudes), some in UTM
(Universal Transverse Mercator), some in state-plane coordinates." To add
to Sloan's headache, each state uses its own state-plane coordinate system.
"In some cases, all we got were Shape files," he says. "Some came with metadata
and projection files. For the ones that didn't, we had to use trial-and-error
to figure out what projections they were based in. That can be a time-consuming
process."

Eventually he was able to import his data into ESRI's ArcMap. When all the
towers were charted, it became clear that whoever was on the phone had been
traveling along the murderer's route.

Using cell phone records and
cell tower locations,
Clay County GIS coordinator Mark Sloan was able to reconstruct
the route traveled by the suspect at the time of the murder.

It's Technology,
Not Magic
"People think of GIS either as Big Brother or magic," says
Sloan, who wants to debunk the myth. He's trying to promote it as a technology
with a lot of potential, especially in judicial proceedings and crime fighting.
It can, for instance, provide historic crime mapping, allowing police officers
to study events over a period of time to identify trends. It can also play
an important role in event planning, for early analysis of the exits, entry
points and security vulnerabilities.

When the trial was over, Sloan found himself at a reception
for those who had worked on the case. "It was mostly law enforcement folks,"
Sloan recalls. Borgen presented Sloan with an honorary memento -- a gold-colored
cell phone -- and a certificate inscribed, "In recognition of outstanding
and dedicated service to the citizens of Clay County in the investigation
and prosecution of the Nasean Jordan murder case."

ABOUT THE AUTHOR
Kenneth Wong is a former editor of Cadence magazine.
He explores innovative use of technology and its implications in GIS Tech
Trends and in Cadalyst magazine’s PLM Strategies column. Reach
him at kennethwongsf@earthlink.net.

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